A device and method are described for draining aqueous humor from the interior of the eye to the exterior of the conjunctiva for reducing intraocular pressure within the eye and, more particularly, an implantable device with a replaceable resistive component is described for regulating the flow of the aqueous humor.
Glaucoma is a group of chronic optic nerve diseases and a leading cause of irreversible blindness. The major risk factor in glaucoma is elevated intraocular pressure due to improper drainage of aqueous humor in the eye. Reduction of intraocular pressure is the only proven treatment to stop the progression of vision loss by reducing stress on the optic nerve.
Standard glaucoma surgeries to reduce intraocular pressure, such as trabeculectomies and glaucoma drainage device implantation, are lengthy and traumatic with unpredictable outcomes and complication rates of 20-60%. Implantable drainage devices function to drain excess aqueous humor from the eye. Installation of a drainage device typically requires a surgical opening made in the sclera to reach the interior of the eye, in particular the anterior chamber or the posterior chamber. The drainage device is then inserted into the interior of the eye for conducting the aqueous humor to the subconjunctival space, herein referred to as subconjunctival shunts, or externally of the conjunctiva, herein referred to as external shunts. A problem associated with subconjunctival shunts is scarring of the bleb in the subconjunctival space affecting its fibrous capsule formation around the outlet, which in many cases requires surgical revision that leads to additional risk of complications. Therefore, there is an ongoing search to identify and utilize alternate drainage sites to avoid many problems associated with bleb and fibrous capsule formations.
External shunts avoid bleb and fibrous capsule formation and the unpredictability of wound healing in the subconjunctival space. However, the outlet of an external shunt may be perceived by the patient as a foreign body, especially those that lie on the corneal surface. These shunts can also be displaced by local tissue motion or extruded by constrictive wound healing processes. One solution secures a subconjunctival portion of the device to the sclera by suturing. However, this technique still leaves the outlet end mobile on the conjunctival surface, which may cause tissue injury and ocular irritation. Moreover, external shunts can expose a mechanical conduit available to transmit microorganisms from the outside to the interior of the eye potentially leading to retrograde infection.
All drainage devices implanted in the eye have the potential to clog from proteins or other substances in the aqueous humor. Clogging reduces permeability of the device and may lead to elevation of intraocular pressure to baseline.
For the foregoing reasons there is a need for a new drainage device for directing aqueous humor from the anterior chamber of an eye to a location external to the eye for reducing and managing intraocular pressure.